EEC IV Trouble Shooting

Tiny
LTXI
  • MEMBER
  • FORD MUSTANG
My vehicle is only "nominally" a Mustang. It is actually a London Coach -- a london taxi Carbodies chassis imported into the US minus engine /transmission and then fitted with a Ford 2.3L engine and C3 automatic. About 150 built before the company went out of business. It is 1985 EEC IV compliant and I buy engine parts for it as a 1985 Mustang. 42,000 miles on the clock.

My immediate problem -- warm summer day with engine warmed up, picked up the throttle coming out of a tight right turn and the engine began choking, sputtering, running ragged, tried to die. Coaxing it home I found I could get it to run ok at 2/3 to WOT after I got it past the unburned fuel. All this very sudden, no issues like this before.

So far -- have replaced plugs, coil, TFI module, and voltage regulator, and pulled the connectors on various sensors just to check. Sometimes car will start and run normally after a day's rest, sometimes not, will always begin to choke, sputter, misfire after warm up and will also always run ok at high / full throttle; open loop. Old plugs were firing clean.

What confuses me most is that if I pull the connector on the external voltage regulator and take the charging system out of the circuit, the car runs just fine. Base engine management / open loop mode I'm sure, but why I haven't a clue. Resistance and voltage checks indicate the alternator appears to be ok.

Also, as you might imagine I'm dealing with much non-standard wiring and I think I've just located the PCM way up under the dash

Any help / assistance / guidance you can provide would be MOST welcome.

-- Don
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Sunday, August 26th, 2007 AT 5:17 PM

6 Replies

Tiny
JACK42
  • MEMBER
Using a voltmeter see if the Alt is throwing A/C current instead of D/C. Happens sometimes will freak out the computer and ignition
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Monday, August 27th, 2007 AT 8:10 AM
Tiny
LTXI
  • MEMBER
What a great answer - makes perfect sense. Got about 25 VAC measured at the input connector to the voltage regulator. Off to find a new alternator. Thank you very much for the help!
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Monday, August 27th, 2007 AT 6:04 PM
Tiny
JACK42
  • MEMBER
Youre welcome
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Tuesday, August 28th, 2007 AT 7:22 AM
Tiny
LTXI
  • MEMBER
Well, it was really great thought, but not the problem. Replaced the alternator with a quality reman and the voltage regulator again with a Wells. When it kept up the problem, I even swapped in a known good battery just for good measure. Problem still exists. Sputters, chokes, stumbles, misfires, runs (barely) ragged, you name it. Pull the plug on the solid state external voltage regulator and it runs good as new. Carb rebuilt and working fine since about three years ago and the fuel is new.

For what it's worth, I'm an aging mechanic and ex-racing wrench who got out of the game before computers took over the world. As you might imagine, this is driving me totally nuts!
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Wednesday, August 29th, 2007 AT 6:35 PM
Tiny
JACK42
  • MEMBER
Is it still throwing a/c voltage? What is the alt charging?
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Thursday, August 30th, 2007 AT 1:04 PM
Tiny
LTXI
  • MEMBER
It appears to be but, I'm beginning to believe that's likely an artifact of my rather ancient analog meter when fed DC on the AC scale. I've changed the alternator and the regulator at the same time. (The original alternator tested good at the store, by the way but I changed it out anyway.) And I've changed the battery. The running, DC charge voltage measured at the battery is right at about 14.6.

If you have any other thoughts, I'd really like to hear them but absent that, I think I've come up with an "easy" solution. Found a local, Denver area, repair shop with a good reputation that semi-specializes in Fords, classics, and muscle cars and appears to appreciate a challenge.
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Thursday, August 30th, 2007 AT 4:41 PM

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